An Unexpected Split-Merge Pathway in the Assembly of the Symmetric Nonribosomal Peptide Antibiotic Closthioamide

Article abstract of DOI:10.1002/anie.202011741

Closthioamide (CTA) is a symmetric nonribosomal peptide (NRP) comprised of two diaminopropane-linked polythioamidated monomers. CTA is biosynthesized by Ruminiclostridium cellulolyticum via an atypical NRP synthetase (NRPS)-independent biosynthetic pathwa

Full text of DOI:10.1002/anie.202011741

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Accepted Article
Title: An Unexpected Split-Merge Pathway to the Symmetric
Nonribosomal Peptide Antibiotic Closthioamide
Authors: Kyle L. Dunbar, Maria Dell, Evelyn M. Molloy, Hannah
Büttner, Jana Kumpfmüller, and Christian Hertweck
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10.1002/anie.202011741
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RESEARCH ARTICLE
An Unexpected Split-Merge Pathway in the Assembly of the
Symmetric Nonribosomal Peptide Antibiotic Closthioamide
Kyle L. Dunbar,[a]+ Maria Dell,[a]+ Evelyn M. Molloy,[a] Hannah Büttner,[a] Jana Kumpfmüller,[a] and
Christian Hertweck*[a,b]
[a]
Dr. K. L. Dunbar, M. Dell, Dr. E. M. Molloy, H. Büttner, Dr. J. Kumpfmüller, Prof. Dr. C. Hertweck
Dept. of Biomolecular Chemistry
Leibniz Institute for Natural Product Research and Infection Biology, HKI
Beutenbergstrasse 11a, 07745 Jena (Germany)
E-mail: christian.hertweck@leibniz-jena.de
[b]
Prof. Dr. C. Hertweck
Faculty of Biological Sciences
Friedrich Schiller University Jena
07743 Jena (Germany)
+ Authors contributed equally.
Supporting information and the ORCID identification numbers for the authors of this article are given via a link at the end of the document.
secondary metabolite isolated from an obligate anaerobe[6] and
Abstract: Closthioamide (CTA) is a symmetric nonribosomal peptide
(NRP) comprised of two diaminopropane-linked polythioamidated
monomers. CTA is biosynthesized by Ruminiclostridium
cellulolyticum via an atypical NRP synthetase (NRPS)-independent
biosynthetic pathway. Although the logic for monomer assembly was
recently elucidated, the strategy for the biosynthesis and
incorporation of the diamine linker remained a mystery. By means of
genome editing, synthesis, and in vitro biochemical assays, we
demonstrate that the final steps in CTA maturation proceed through
a surprising split-merge pathway involving the dual use of a
thiotemplated intermediate. This pathway includes the first examples
of an aldo-keto reductase catalyzing the reductive release of a
thiotemplated product, and of a transthioamidating transglutaminase.
In addition to clarifying the remaining steps in CTA assembly, our
data shed light on largely unexplored pathways for NRPS-
independent peptide biosynthesis.
a thioamidated natural product.[7] CTA is comprised of two p-
hydroxybenzoic acid (PHBA)-end-capped β-alanine (βAla)
polymers linked through diaminopropane (DAP, Figure 1A).[3c, 4]
Recently,
a combination of knockout studies and in vitro
biochemical assays illuminated the type II peptidyl carrier protein
(PCP)-dependent assembly of the polythioamidated backbone of
8]
CTA from L-aspartate and chorismate (1; Figure 1C).[3a,
However, the biosynthetic steps for the synthesis and
incorporation of the DAP linker remained unclear. Here, we
elucidate the final steps in CTA maturation using a combination
of genome editing, in vitro biochemical assays, and chemical
synthesis.
Results and Discussion
Of the eleven biosynthetic proteins encoded in the CTA
biosynthesis gene cluster, three remained to be functionally
characterized: a putative pyridoxal phosphate (PLP)-dependent
aminotransferase (CtaB), an aldo-keto reductase (AKR; CtaK),
and a transglutaminase (CtaJ; Figure 1B and 1C).[8b] Based on
previous knockout studies[3a] and the activities of characterized
transglutaminases,[9] we predicted that CtaJ would be
responsible for incorporating the DAP linker into the CTA
backbone. However, the source of this diamine core was
unknown. In bacteria, DAP is biosynthesized from L-aspartate
semialdehyde by the sequential function of a PLP-dependent
Introduction
Nonribosomal peptides (NRPs) are
a
diverse class of
ecologically and medicinally important secondary metabolites.
The majority of NRPs are assembled by either multi-modular
(Type I) or stand-alone (Type II) NRP synthetases (NRPSs).[1] In
both cases, the NRPSs function in a thiotemplated manner on
substrates covalently attached to carrier proteins and assemble
peptides in linear assembly lines. In addition to these canonical
systems, NRPS-independent biosynthetic pathways are
known.[2] NRPS-independent systems often rely on amide
synthases that are homologs of enzymes involved in primary
metabolic pathways including, but not limited to, members of the
ATP-grasp, cysteine protease, and acyl-CoA ligase protein
families.[2] In contrast to NRPSs, these atypical amide synthases
typically do not follow the canonical thiotemplated program for
NRP assembly, but rather act on free substrates.[2] A notable
deviation from this trend is exemplified by the NRPS-
independent, yet thiotemplated biosynthesis of the DNA gyrase-
targeting antibiotic closthioamide (CTA; Figure 1A and 1B).[3]
CTA is a symmetric perthioamidated NRP produced by the
obligate anaerobic bacterium Ruminiclostridium cellulolyticum.[3c,
aminotransferase and
a
decarboxylase.[10] Although the
presence of CtaB and a PLP-dependent decarboxylase (CtaF) in
the genetic locus is consistent with such a pathway, we recently
demonstrated that CtaF is involved in the assembly of the poly-
βAla backbone of CTA (Figure 1C).[8a] Thus, we predicted that
the diamine core of CTA would originate from a novel pathway
involving CtaB and the AKR CtaK.
Based on the bioinformatically predicted activities of CtaB
(Figure S1 in the Supporting Information) and CtaK (Figure S2),
we envisioned two possible linear pathways for DAP production
and incorporation into CTA (Figure 1C). In the first pathway (i in
Figure 1C), the terminal βAla of PCP-linked 1 (CtaE-1; Figure
1C) would be converted to DAP by the sequential action of CtaK
and CtaB to afford 2. CtaJ would then merge two molecules of 2
4]
This potent copper chelator[5] is a rare example of both a
1
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10.1002/anie.202011741
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RESEARCH ARTICLE
into
CTA,
releasing
DAP
in
the
mass (calc. m/z 385.1185 [M+H]+; found m/z 385.1193
Figure 2. In vivo dissection of the final steps in CTA maturation. HPLC profiles
(270 nm absorbance) of extracts from cultures of R. cellulolyticum wild-type
(WT) and mutant strains and the structures of the CTA congeners identified in
the extracts. An HPLC profile of a synthetic reference compound of 2 is
displayed for comparison. PHBA, p-hydroxybenzoic acid; CTA*, CTA
degradation product lacking
a single thioamide; #, unrelated metabolite.
[M+H]+) and isotope pattern consistent with 2 was detected
(Figure 2 and Figures S3–S4). Due to low production titers,
attempts to isolate sufficient quantities of the compound for
structure elucidation by NMR were unsuccessful. Therefore, we
synthesized
characterized compound as
2
(Supporting Information) and used this
reference. The unknown
a
metabolite has the same retention time and MS2 fragmentation
pattern as the reference (Figure 2 and Figure S3 and S5),
demonstrating that 2 is indeed produced by R. cellulolyticum.
Figure 1. Closthioamide biosynthesis gene cluster and proposed routes to
diaminopropane incorporation. A) Structure of closthioamide (CTA) with
diaminopropane (DAP) core colored red. B) CTA biosynthesis gene cluster.
PHBA; p-hydroxybenzoic acid. C) Proposed CTA biosynthetic pathway. Steps
that have been previously characterized are outlined in a green box while the
uncharacterized portion of the pathway is outlined in a grey box. Two possible
routes (i and ii) for DAP formation and incorporation are displayed.
The origin of
2 differs between the two putative
biosynthetic routes for DAP formation and incorporation (Figure
1C). While both pathways predict that CtaB and CtaK are
required for the formation of 2, its production is only dependent
on CtaJ in pathway ii. To interrogate the roles of CtaB, CtaJ,
and CtaK in the production of 2 and CTA, we used CRISPR-
Cas9-mediated genome editing[11] to generate mutant R.
cellulolyticum strains harboring inactivated versions of the
corresponding genes (R. cellulolyticum ΔctaB, ΔctaJ,[3a] and
ΔctaK; Figure S6–S7) and analyzed their metabolite profiles by
HPLC-HRMS (Figure 2 and Figure S3). R. cellulolyticum ΔctaB
produces low levels of CTA in addition to a suite of known
derivatives and intermediates (compounds 1–5; Figure 2),
demonstrating that the aminotransferase is not essential for CTA
production, likely due to genetic redundancy. In contrast, CTA
biosynthesis is abrogated in R. cellulolyticum ΔctaJ[3a] and R.
cellulolyticum ΔctaK (Figure 2). R. cellulolyticum ΔctaK also lost
the ability to produce 2 and closthioamide F (3), and instead
process. In the second pathway (ii in Figure 1C), DAP could be
generated as a free diamine by the CtaK-dependent reduction
and CtaB-dependent transamination of an unknown primary
metabolite. CtaJ would cleave the terminal thioamide CtaE-1,
releasing CtaE-linked βAla (CtaE-βAla), and transfer the PHBA-
containing fragment to DAP to produce 2. CtaJ would then
further process this new intermediate using a second equivalent
of CtaE-1 to produce CTA and CtaE-βAla.
Although 2 is a predicted intermediate of both pathways
(Figure 1C), it has not previously been detected from R.
cellulolyticum cultures.[3a, 3c, 4] Upon growth of R. cellulolyticum
under CTA-producing conditions, a metabolite with an exact
2
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Figure 3. CtaB, CtaK and CtaJ work together to convert CtaE-1 to CTA in a split-merge pathway. A) HPLC profile (255 nm absorbance) of CtaB reactions
performed with Cbz-propionaldehyde and various amine donors. A synthetic reference compound of the expected product, 6, is displayed for comparison. Lys,
lysine; Cad, cadaverine; Spd, spermidine; Arg, arginine; Gab, γ-aminobutyric acid. B) HPLC profiles (270 nm absorbance) of CtaJ reactions. A synthetic reference
compound of CTA is displayed for comparison. C) Split-merge pathway for the conversion of CtaE-1 to CTA. D) MALDI-TOF-MS spectral overlay of CtaJ
reactions. The average masses of CtaE-1 and CtaE-βAla are indicated. The red asterisk denotes holo-CtaE formed from thioester hydrolysis. A, B, D) Red
strikethrough = heat-inactivated enzyme.
produces increased levels of 1 (closthioamide G), closthioamide
H (4), and closthioamide M (5) (Figure 2 and Figure S3). The
CtaJ-deficient strain no longer assembles 4 and 5 but produces
increased levels of 1, 2, and 3 (Figure 2 and Figure S3). The
metabolite profiles of the mutant strains, in particular the
continued production of 2 by R. cellulolyticum ΔctaJ, strongly
support pathway i. Furthermore, CtaK is implicated in the
III aminotransferases that use diamines, β-amino acids, and γ-
amino acids as amine donors.[14] Therefore, we assayed a
diverse set of potential amine donors and monitored reaction
progress by HPLC-HRMS. In all assays performed with CtaB
and a diamine-containing co-substrate, we detected a new
compound with an exact mass (calc. m/z 209.1285 [M+H]+;
found m/z 209.1284 [M+H]+), MS2 fragmentation pattern, and
elution time consistent with a synthetic reference compound of
the expected aminated product (6; Figure 3A and Figure S10–
S12). To ascertain the preferred amine donor for CtaB, we first
performed reaction time courses with all substrates that were
accepted in the initial screen (Figure S13) and then subjected
the top three amine donors – lysine, putrescine and cadaverine
– to a detailed kinetic investigation (Figure S14). Although the
kinetic profiles obtained for each substrate were quite similar,
the specificity constant for lysine was 5-fold and 10-fold greater
than the constants obtained for cadaverine and putrescine,
respectively. Combined with the observation that cadaverine and
putrescine titers are low when R. cellulolyticum (Figure S15) is
grown under CTA production conditions, we concluded that
lysine is the preferred amine donor for CtaB.
reductive release of
1 from CtaE. Although common in
secondary metabolite pathways, the reductive release of
thiotemplated products is performed by members of the short-
chain dehydrogenase protein family,[12] making CtaK the first
AKR protein family member identified to date that catalyzes the
reduction of a thioester.[13]
With a putative pathway identified for the assembly and
introduction of the DAP linker, we sought to reconstitute the
activities of the implicated enzymes in vitro. As such, CtaB, CtaK
and CtaJ were heterologously produced as an N-terminal His6-
tagged fusion protein in Escherichia coli. Although CtaK was not
soluble under any of the production conditions tested, we were
able to obtain sufficient quantities of CtaB and CtaJ (Figure S8)
for in vitro biochemical assays.
CtaB is predicted to be a PLP-dependent aminotransferase
responsible for the conversion of AH-1 to 2 (Figure 1C). Since
the poor solubility of CtaK precluded the in situ enzymatic
generation of the native substrate from 1, we performed in vitro
assays with an aldehyde surrogate of AH-1 (Figure 3A). Assays
were supplemented with PLP, since CtaB did not co-purify with
high levels of the cofactor (Figure S9). Phylogenetic analysis
(Figure S1) indicated that CtaB is most closely related to class-
With the aminotransferase function of CtaB assigned, we
proceeded to characterize the activity of CtaJ. We expected that
CtaJ would convert two molecules of 2 into CTA, producing DAP
as a byproduct. Therefore, reactions were performed with CtaJ
and synthetically prepared 2, and CTA production was
monitored by HPLC-HRMS. Although the metabolite profiles of
the knockout strains (Figure
compelling evidence that
2
and Figure S3) provided
2
is an intermediate in CTA
3
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RESEARCH ARTICLE
was observed in the chromatogram of the SNAC-1 reaction. The
exact mass (calc. m/z 764.1679 [M-H]-; found m/z 764.1682 [M-
H]-), isotope pattern, and MS2 fragmentation pattern of the
corresponding molecule suggested that it is a CTA congener
bearing an additional βAla residue (Figure S18–S19). We expect
that this is formed by the non-specific cleavage of the thioester
of SNAC-1 by CtaJ and attachment of the corresponding
intermediate to 2. Attempts to increase SNAC-1 turnover by the
addition of CaCl2 or GTP were unsuccessful (Figure S17),
demonstrating that the activity of CtaJ, like other bacterial
transglutaminases,[9c] is calcium- and GTP-independent.
As turnover was very low in the assays performed with
SNAC-1, we sought to improve turnover by using the predicted
in vivo substrate, CtaE-1. Therefore, we synthesized coenzyme
A-linked 1 (CoA-1), purified His6-tagged apo-CtaE from E. coli
(Figure S8), and loaded the substrate onto apo-CtaE using the
promiscuous phosphopantetheinyl transferase Sfp.[15] CtaJ
reactions were then performed with CtaE-1 and 2, and reaction
progress was monitored by HPLC-HRMS. In contrast to the low
level of CTA detected in assays containing the SNAC thioester
(Figure S17), we observed robust production in assays
supplemented with CtaE-1 (Figure 3B). When CtaJ or either
substrate was omitted, CTA production was lost. Furthermore,
consistent with the split-merge biosynthetic model, substituting 2
with DAP also abrogated CTA production (Figure S20). However,
in reactions performed with CtaE-1 alone, 4 and a derivative of 4
harboring a terminal thioacid (7) were produced (Figure 3B and
Figure S21–S22). This result is consistent with a mechanism
where CtaJ cleaves the terminal thioamide of CtaE-1 and
attaches the PHBA-containing fragment to 2 (Figure 3C). To
corroborate this model, we monitored the fate of CtaE-1 by
matrix-assisted laser desorption/ionization-time-of-flight-mass
spectrometry (MALDI-TOF-MS) and found that, regardless of the
presence or absence of 2, CtaJ converts CtaE-1 to a new
species with a mass consistent with the expected βAla adduct
(Figure 3D). Taken together, these results demonstrate that
CtaJ is a thiotemplated transthioamidase that synthesizes CTA
by coupling CtaE-1 and 2.
Figure 4. CtaJ uses the catalytic triad of canonical transglutaminases. A)
General mechanism of canonical transglutaminases. B) HPLC profiles (270
nm absorbance) of CtaJ reactions performed with wild-type or mutant CtaJ. C)
MALDI-TOF-MS spectral overlay of CtaJ reactions performed with wild-type or
mutant CtaJ. The red asterisk denotes holo-CtaE formed from thioester
hydrolysis.
biosynthesis and the substrate for CtaJ, no processing of 2 was
detected in the enzyme assays (Figure 3B and Figure S16).
While bacterial transglutaminases are not known to require any
cofactors or additives for activity,[9c] the activity of some
mammalian transglutaminases is allosterically regulated by
calcium and guanosine triphosphate.[9a] As such, we also
performed assays with CaCl2 and GTP supplementation;
however, regardless of the reaction conditions, the processing of
2 was not observed (Figure S16).
Surprised by the inability of CtaJ to convert 2 to CTA, we
reevaluated our biosynthetic model. Our initial assumption was
that the pathway proceeded in a linear fashion, akin to canonical
thiotemplated systems.[1] However, we realized that the data are
also consistent with an atypical branching pathway where CtaE-
1 is a substrate for both CtaK and CtaJ (Figure 3C). In the first
branch, CtaE-1 would be converted to 2 by the sequential action
of CtaK and CtaB as initially proposed. In the second branch,
CtaJ would cleave the terminal thioamide of CtaE-1 to generate
an enzyme-bound intermediate (CtaJ-7) and CtaE-βAla. The
pathways would then merge with the CtaJ-dependent transfer of
7 to 2, affording CTA without the production of DAP.
As an initial test for the feasibility of this branching
biosynthetic route, we grew R. cellulolyticum under CTA-
producing conditions and checked for the accumulation of DAP.
Consistent with this new proposal, no DAP was detected (Figure
S15). Encouraged by this result, we synthesized 1 and an N-
acetyl cysteamine thioester of 1 (SNAC-1) and repeated the
CtaJ assays with the addition of these potential substrates.
HPLC-HRMS analysis of the reactions demonstrated that low
levels of CTA were only formed in assays containing SNAC-1, 2,
and CtaJ (Figure S17). The removal of any of these components
or the substitution of SNAC-1 with 1 led to a complete loss of
CTA production. Furthermore, in addition to CTA, a new peak
Over the course of our studies, we noticed that
–
irrespective of the reaction time used – we never achieved
complete consumption of the CtaE-1 precursor. Furthermore,
the processing of CtaE-1 decreased in reactions performed with
2 relative to assays lacking 2 (Figure 3D). We therefore
suspected that the activity of CtaJ might be strongly product
inhibited. Indeed, when we added CTA to CtaJ assays we
observed a substantial decrease in CtaE-1 processing by
MALDI-TOF-MS (Figure 3D and Figure S23). From a biological
perspective, this pronounced product inhibition is unsurprising,
as a buildup of CTA in the cell would be indicative of a failure in
the transport machinery. Under such conditions, the negative
regulation of CtaJ activity by CTA could prevent the self-
poisoning that would presumably arise from the continued
synthesis of CTA.
Transglutaminases typically catalyze the inter- and intra-
molecular crosslinking of glutamine and lysine residues on
9c]
proteins and peptides.[9a,
Apart from CtaJ, only one other
transglutaminase has been reported that catalyzes the
thiotemplated formation of an amide bond, an enzyme involved
in the biosynthesis of the acylated NRP andrimid, AdmF.[9b]
However, AdmF cleaves a thioester, not a thioamide linkage.
Given the unprecedented nature of the transthioamidation
4
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10.1002/anie.202011741
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RESEARCH ARTICLE
reductively releases the perthioamidated intermediate from CtaE,
and CtaB converts the corresponding aldehyde, AH-1, to 2 in a
diamine-dependent reaction. In a separate branch, CtaJ cleaves
the terminal thioamide of CtaE-1 forming an enzyme-bound
intermediate (CtaJ-7) and CtaE-βAla. The two pathways
converge with the transfer of 7 from the active site cysteine of
CtaJ to 2, affording CTA. The CtaE-βAla byproduct is then
recycled by the upstream enzymes to form CtaE-1. This
unexpected split-merge pathway relies on the conversion of the
terminal βAla residue to DAP in one branch, and its use as a
recyclable priming residue in the other (Scheme 1). In this way,
an elegant solution is provided for the biosynthesis of a
symmetric molecule from an asymmetric pathway without the
production of unused byproducts. Notably, the deconvolution of
these final steps in CTA assembly not only assigns roles to each
of the biosynthetic enzymes encoded in the biosynthetic operon
but also accounts for all known intermediates and congeners
(Scheme S1).
In type I thiotemplated biosynthetic pathways the carrier
protein is covalently linked to the biosynthetic machinery and, as
a consequence, each intermediate is typically passed directly to
16]
a
single downstream enzyme in a
linear fashion.[1a,
Biosynthetic pathways utilizing stand-alone type II carrier
proteins do not face the same structural constraints and often a
single carrier protein can be recognized by multiple enzyme
17]
partners.[1b,
This behavior is effectively illustrated by the
association of CtaE with six biosynthetic enzymes over the
course of CTA maturation. Despite this inherent flexibility, type II
thiotemplated pathways typically proceed in a linear fashion,
with split-merge pathways, like the one described here, being
remarkably rare.[1a, 16, 18] The discovery of split-merge logic in the
CTA maturation pathway highlights the flexibility of type II
thiotemplated biosynthetic machinery and presents novel
opportunities for pathway engineering.
Scheme 1. Complete pathway for CTA biosynthesis featuring an unusual split-
merge route.
Conclusion
reaction catalyzed by CtaJ, we next sought to gain deeper
mechanistic insights. Transglutaminases are members of the CA
In summary, we have unraveled the final steps of CTA
maturation and discovered an unusual split-merge assembly
strategy for the synthesis and incorporation of the DAP linker. In
the process, we have not only uncovered the first example of a
transthioamidase but also implicated an AKR protein family
member in the reductive release of a thiotemplated product. The
identification of these non-canonical members of well-
characterized protein families highlights novel enzyme functions
that can be found through the investigation of atypical
biosynthetic pathways.
clan of proteases and, accordingly, typically have a Cys-His-Asp
9c]
catalytic triad.[9a,
For canonical transglutaminases, the
transamidation reaction proceeds via a covalent intermediate
with the catalytic cysteine residue (Figure 4A). Despite the large
sequence divergence between CtaJ and characterized members
of the transglutaminase protein family, a putative catalytic triad is
present in CtaJ (Cys114, His148, Asp165; Figure S24). We
generated mutant versions of CtaJ bearing alanine substitutions
to the residues of the putative catalytic triad (CtaJC114A, CtaJH148A
and CtaJD165A; Figure S8) and tested their catalytic competency.
Consistent with the bioinformatic prediction, all CtaJ mutants
were impaired in CTA production and CtaE-1 processing (Figure
4B–4C). These data demonstrate that the CtaJ uses the
standard catalytic triad of the transglutaminase protein family to
catalyze the transthioamidation reaction.
,
Acknowledgements
We thank A. Perner, T. Kindel and M. García-Altares Peréz for
MS measurements and H. Heinecke for NMR measurements. K.
Dunbar was supported by the Humboldt Research Fellowship for
Postdoctoral Researchers. Financial support by the DFG
(Leibniz Award to C. Hertweck) is gratefully acknowledged.
Based on the results described herein, we propose a model
for the complete biosynthetic pathway to CTA (Scheme 1). The
biosynthesis begins with the conversion of chorismate to PHBA
by CtaA and the assembly of the amide backbone on CtaE
(CtaE-amido-1) by CtaD and CtaF-G.[3a, 8a] Next, CtaE-amido-1,
is iteratively thioamidated by CtaC to afford CtaE-1.[8b] The
pathway branches at this point. In one branch, the AKR CtaK
Conflict of Interest
The authors declare no conflict of interest
5
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Keywords: antibiotics • biosynthesis • enzymes • natural
products • thioamide
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This article is protected by copyright. All rights reserved.

10.1002/anie.202011741
Angewandte Chemie International Edition
RESEARCH ARTICLE
Entry for the Table of Contents
Splitting up to come together. Closthioamide is a symmetric perthioamidated nonribosomal peptide (NRP) produced by an atypical
NRPS-independent biosynthetic pathway. Using a combination of genome editing and in vitro biochemical assays we elucidated the
last steps of closthioamide biosynthesis and found an unexpected asymmetrical route involving novel enzyme functions for members
of the aldo-keto reductase and transglutaminase protein families.
Institute and/or researcher Twitter usernames: @LeibnizHKI @Hertweck_Lab
ORCID Numbers
Kyle L. Dunbar: https://orcid.org/0000-0002-7410-5169
Maria Dell: https://orcid.org/0000-0003-2718-2409
Evelyn M. Molloy: https://orcid.org/0000-0001-8822-7207
Hannah Büttner: https://orcid.org/0000-0002-0510-9086
Jana Kumpfmüller: https://orcid.org/0000-0003-3510-8276
Christian Hertweck: https://orcid.org/0000-0002-0367-337X
7
This article is protected by copyright. All rights reserved.